The present invention relates to the production/manufacturing of custom liners for use with prosthetic limbs of various type. More specifically, the present invention relates to a system and method of manufacturing custom prosthetic liners, whereby a prosthetist or other qualified practitioner can capture the shape of an amputee's residual limb, manipulate data relating to said shape, if desired, and transmit or otherwise provide said data to a manufacturing facility that is equipped to receive the data and to manufacture a custom prosthetic liner therefrom.
While there are various types of prosthetic limbs, the most common are likely those designed to replace some portion of an arm or leg. While a liner manufactured by the system and method of the present invention will work equally well in either application, for purposes of simplicity, we will confine the immediately following discussion of the present invention and relevant known technologies primarily to that of a prosthetic leg. From this discussion, it can be understood that the system and method of the present invention offers advantages not available with known systems and methods for producing prosthetic liners—regardless of the specific type of liner produced.
Most prosthetic legs may be categorized as either below knee (BK), or above knee (AK) prosthetics. A BK prosthetic leg is designed to fit an amputee whose residual limb terminates at some point below the knee joint (i.e., the knee joint is still present). BK amputations are often referred to as transtibial amputations, as the amputation point passes through the tibia of the lower leg. An AK prosthetic leg is designed to fit an amputee whose residual limb terminates at some point above the knee joint (i.e., the knee joint has been removed). AK amputations are often referred to as transfemoral amputations, as the amputation point passes through the femur of the upper leg. Other categories of prosthetic legs include Symes, knee disarticulations, and hip disarticulations.
Whether a prosthetic leg is designed for a BK or an AK amputee, the leg will generally have some common components. For example, a BK prosthetic leg will generally have an upper portion comprising a socket that is provided to receive a portion of the amputee's residual limb. To the bottom of the socket is typically affixed a lower portion, normally comprising an upright assembly of some type that is connected to a foot or ground-contacting portion. During initial development of prosthetic legs, the upright assembly may simply have been a rod or similar structure used to impart the prosthetic leg with the proper length. A foot or similar structure may not even have been included. Modern BK prosthetic legs may make use of more complex upright assemblies that may provide for damping or other desirable properties. The upright assembly portion of a BK prosthetic leg may also be shaped to simulate the appearance of a real leg.
AK prosthetic legs will also generally have an upper, socket portion, that is provided to receive a portion of the amputee's residual limb. An AK prosthetic limb will also typically have a lower portion attached to the bottom of the socket. Normally, the lower portion of an AK prosthetic limb will also have an upright assembly of some type that is connected to a foot or ground-contacting portion. Older AK prosthetic limbs sometimes incorporated a rudimentary type of pivoting assembly to connect the lower portion to the socket. This allowed the amputee to swing the lower portion of the prosthetic limb forward during walking, in an attempt to simulate the amputee's natural gait. Modern AK prosthetic limbs are typically more complicated. For example, hydraulic or pneumatic cylinders, or some other type of damping device may be provided at the knee joint to better control the bending thereof.
Whether the prosthetic leg in question is of the BK or AK type, and whether the leg is simple or complex in design, acceptable use thereof still depends to a great extent on the fit of the amputee's residual leg into the socket of the prosthetic leg. No matter how well the prosthetic leg is otherwise designed, if the fit of the residual leg within the socket is not adequate, the prosthetic leg may irritate the residual leg, cause pain to the amputee, and/or may not be adequately retained. Thus, without a proper fit of the residual leg to the socket, a prosthetic leg can be substantially unusable.
In the early days of prosthetics development and manufacture, amputees had little choice as to how a prosthetic leg was fit and retained on the residual limb. For example, at one time, both BK and AK amputees had to rely on a “skin fit,” whereby the skin of the residual leg produced a seal against the inner surface of the socket. In this retention method, at least a portion of the air in the socket is displaced by the residual leg during donning of the prosthetic leg. The displacement of air ideally creates a vacuum within the socket that retains the prosthetic leg on the residual leg. The seal between the skin and the inner surface of the socket is crucial to preventing air from entering the socket and, therefore, maintaining the vacuum.
There are numerous problems with a skin fit, however. Most notably, the constant contact of the skin against the hard inside surface of the socket can become painful, and can also cause problems with the skin of the residual leg. For example, the fit of the socket against the residual leg may press on nerves or other sensitive spots thereof. This problem may be exacerbated when the residual leg has little flesh, or exhibits particularly bony areas. Also, the skin of the residual leg may become irritated, chapped or raw, or may otherwise develop sore spots, lesions, or similar areas of weakness due to its contact with the socket. A skin fit may also cause the residual leg to perspire, jeopardizing the seal between the residual leg and socket, and further contributing to problems with the amputee's skin. Additionally, when employing a skin fit, powders, gels, or other similar lubricants are typically required to be spread over the residual leg and/or the inner surface of the socket in order to allow the residual leg to be properly inserted therein. Such surface modifiers are not only messy, they may be uncomfortable, and may further contribute to problems with the skin of the residual leg.
To alleviate the above-described problems, attempts have been made to produce a covering that may be placed over the residual leg prior to its insertion into the prosthetic leg socket. These attempts initially involved only BK prosthetics. The first such coverings developed for this purpose are best characterized as socks. These socks were typically manufactured of a fabric material of some thickness, which could be pulled over the distal end of the residual leg prior to its insertion into a socket. Such socks were problematic, however, particularly because they often lacked adequate comfort and secure suspension.
In an attempt to overcome the deficiencies of the sock-type liner, a silicone liner was introduced. This initial silicone liner was offered in the form of a kit. Before employing the kit to produce a liner, it was first necessary to produce a mold of the amputee's residual leg. This was typically accomplished by creating a cast of the residual leg, and then filling the cast with plaster or some other material to create a positive mold. The materials provided in the kit could then be mixed together in a lab, and somehow applied to the outer surface of the mold. As can be imagined, this process is cumbersome, messy, and likely produces a liner of substantially less than uniform thickness. The liner also could not simply be purchased from a supplier but, rather, had to be produced by a prosthetist or other practitioner qualified to cast the residual leg and subsequently produce the liner. In addition, a liner produced using this kit was required to be attached to a prosthetic leg via a pin connection, as a suction fit between the liner and the socket was not attainable. Moreover, as silicone tends to cling to other materials, a lubricant was again typically required to allow its insertion into a prosthetic leg socket.
A generic silicone liner was next developed, which liner dispensed with the necessity of purchasing a kit of materials and handcrafting a liner therefrom. This liner consisted substantially of a roll-on silicone sleeve. A few different sizes of the sleeve were produced, and the practitioner was required to select the size which most closely approximated the size of the amputee's residual leg. This generic silicone sleeve was designed primarily to allow for improved suspension (retention) of a prosthetic leg on a residual leg via a mechanical pin lock. Unfortunately, because the residual leg can be of virtually unlimited size and shape, it was often difficult to select a liner that fit acceptably. Additionally, similar to its predecessor, this liner required that powder be applied to the residual leg, to the outer surface of the liner, or both, in order to facilitate donning of the liner and insertion thereof into a prosthetic leg socket.
Next introduced was what may be accurately described as a gel sock. As opposed to the silicone material of two of the aforementioned liners, this gel sock was manufactured by dipping a former into a gel material. The gel sock was very thin and offered no means of suspension. The thin construction also provided for little cushioning. Another substantial disadvantage of the gel sock was that it commonly caused adverse reactions of an amputee's skin when worn. This is believed to be the result of the gel material itself, which is thought to have been solvent-based.
A urethane liner was subsequently introduced, which liner alleviated some of the problems inherent to the above-described liners. Unfortunately, this urethane liner had problems of its own. First, a prosthetist was again required to make a cast or mold of an amputee's residual leg, which cast or mold had to be thereafter sent to the sole company that produced the liners. Because the manufacturing process associated with this liner is relatively slow, it often took weeks to receive the liner after sending out the cast or mold. These urethane liners were generally also substantially thicker than the liners previously described. Because the urethane material has a much higher density, these liners were also typically much heavier than the preceding liners. A further drawback associated with this liner and liner manufacturing method is the fact that the liner manufacturer must keep a positive mold of the amputee's residual leg if additional liners are to be made for that amputee in the future. As the typical mold was made from plaster, such molds are generally, fragile, and take up a not insubstantial amount of space. Yet another drawback was that this system was not compatible with a pin suspension. Additionally, similar to several of the aforementioned previously known liners, the amputee's residual leg generally had to be lubricated prior to donning the urethane liner.
It should be realized, that in addition to the illustrated deficiencies inherent to the aforementioned previously known liners, such liners were also typically only available for use with BK prosthetics. In fact, to the best of the Applicant's knowledge, no form of liner was available for use with AK prosthetics until approximately the mid-1990's, and the use of liners with AK prostheses employing suction retention did not gain acceptance until approximately 2001.
The Applicant currently manufactures and sells a liner that is substantially superior to those liners discussed above. The Applicant's current liner, known commercially as the Alpha® liner, is available to amputees as an off-the-shelf product. This liner is generally manufactured from a novel block copolymer material to which is adhered a fabric covering. The fabric-covered liner is easily rolled onto the residual leg or arm, with the fabric material facing out. The fabric material allows for easy donning and doffing of a prosthetic limb, as the inner surface of the prosthetic limb socket slides easily over the fabric. The fabric material also improves the durability, stability, and cosmetic appearance of the liner. In comparison to the aforementioned liners, the Applicant's existing liner is generally longer, with the block copolymer material typically extending substantially to the edge of the fabric that typically extends beyond the brim of the socket. The design of the Applicant's existing liner offers superior cushioning, better prevents air entry, and reduces the chances of perspiration forming around the portion of the residual limb that resides within the prosthetic limb socket. Also, the particular block copolymer material used allows the liner to better conform to the shape of the amputee's residual limb, and may contain additives, such as mineral oil, which act to condition the skin.
In a similar manner to the aforementioned and previously known liners, however, the Applicant's present liner has been heretofore available in only a few standard sizes. Thus, an amputee has up until now been required to order an Alpha® liner of a size that most closely approximates the size of their residual limb. Due to its design and construction, such an off-the-shelf Alphas liner still typically provides for a comfortable fit—and is still generally superior to previous liners. This is due in part to the ability of the Alpha® liner to conform to the shape of an amputee's residual limb as the liner is worn. However, the ability to manufacture such a liner that is also customized to fit an individual amputee remains desirable, as such a custom liner would provide for an even further improvement in fit, and may be especially beneficial to amputees who have, for example, highly sensitive, bony, or unusually shaped residual limbs.
For certain of the reasons described above with respect to known prosthetic liners, as well as for other reasons, it has up until now been impractical to produce a custom liner. For example, using typical known techniques would require the plaster casting of an amputee's residual limb, the production therefrom of a positive replica of the residual limb, and storage of the positive replica to allow for the production of future liners. In addition, it would be extremely cost prohibitive to manufacture a liner mold designed specifically to account for the peculiarities of each amputee's residual limb.
The system and method of the present invention overcomes the aforementioned problems and allows the manufacture of a custom prosthetic liner of any type (i.e., leg, arm, etc.) in a timely and cost efficient manner. The system and method of the present invention eliminates the need to cast an amputee's residual limb in order to obtain the accurate shape thereof. Rather, one embodiment of the system and method of the present invention can obtain the accurate shape of an amputee's residual limb by making use of a shape capture device to capture the 3-dimensional shape of the residual limb with a high degree of accuracy, or through the application of measurements to a shape template. Software associated with the shape capture device may optionally be used to convert the 3-dimensional shape (image) into a 3-dimensional electronic model that accurately represents the residual limb. Alternatively, the software associated with the shape capture, or other software, can apply measurements to a shape template to produce a 3-dimensional electronic model that represents the residual limb. The software, through an interface, preferably also allows a prosthetist or other qualified practitioner to produce a 3-dimensional electronic model of a liner that makes use of the exterior shape of the residual limb to calculate its interior geometry. The liner model can be generated regardless of whether a residual limb model has been generated. If used, the practitioner can modify the residual limb model in order to further fine-tune the fit of the liner that will be produced therefrom. Once the liner model is deemed to be in acceptable form, the data associated therewith is transmitted or otherwise provided to a manufacturing facility that is equipped to receive the data and to produce a liner therefrom. In one embodiment of the present invention, the data is used to produce a 3-dimensional positive likeness of the (modified or unmodified) residual limb from a selected material. The 3-dimensional positive likeness of the residual limb can then be used as a mold core in conjunction with a standard (existing) liner mold cavity to produce a custom prosthetic liner. Thus, this embodiment of the system and method of the present invention does not require the use of a wholly unique liner mold in order to produce the custom liner. In another embodiment of the present invention, the data may be used to produce unique positive (core) and negative (cavity) portions of a liner mold. In this embodiment of the present invention, the whole of each mold is then unique to a particular amputee. While this method is likely more costly than the previously described method, it is contemplated that such molds could be manufactured of low cost materials, as such molds are not likely to experience a high number of molding cycles.
The system and method of the present invention may be utilized by having an amputee visit, for example, a prosthetist or other practitioner's office, wherein the shape capture of the amputee's residual limb and the optional modification of the subsequently generated electronic model may take place. Alternatively, the shape capture device may be transported to the location of the amputee. In this case, the captured shape of the residual limb can be converted to a 3-dimensional model and optionally modified while at the amputee's location, such as through the use of a laptop, pen, or pocket computer, or a personal data assistant (PDA), or the captured shape of the residual limb may be saved for later processing at a different location. The finalized data representing the electronically modelled residual limb can be delivered to a qualified manufacturing facility in any number of ways, such as, for example, by delivery on a machine readable storage medium, by wired or wireless transmission over the Internet, or by direct transfer from machine to machine (such as, for example, from a laptop computer to another computer, or to a CNC or similarly controlled machining device). In an alternate embodiment of the present invention, a conventional plaster cast of the residual limb can be taken, and the cast subsequently digitized to obtain an electronic model of the residual limb. This embodiment of the present invention may be practiced, for example, when a cast of the residual limb already exists, or when a practitioner prefers to continue working with plaster.
In any event, the system and method of the present invention allows an amputee to easily acquire a prosthetic liner that is customized to fit his/her residual limb, thereby providing for maximum comfort and support. Further, the first and subsequent custom liners can be ordered from the manufacturer(s) in the same manner as other prosthetic supplies, and can be delivered to the amputee in a timely manner and at a reasonable price. The system and method of the present invention also makes the storage of residual limb casts or molds optional, as the data required to produce the liner can be stored in electronic form. The system and method of the present invention may further permit a prosthetist or other qualified practitioner to specify options for inclusion on the liner, such as, for example: different types of suspension components and their size, location and orientation; bladders (including inflatable bladders) and their location and size; liner materials and material properties, including hardness, elasticity; the inclusion of additives, such as anti-microbials, therein; liner cover properties; and, sensors and their type and location. Additionally, the system and method of the present invention may allow for the manufacture of a custom liner that permits an amputee whose residual limb size/shape has changed, to continue using his/her existing socket. Similarly, it may be possible to produce custom liners that allow amputees to use a generic socket, with the difference in shape being accounted for by the liner, thereby greatly reducing the overall cost of a prosthetic limb. Therefore, as can be seen from the foregoing discussion, and as can be even better understood from a reading of the following detailed description of exemplary embodiments, the system and method of the present invention permits the practical manufacture of a custom prosthetic liner that has not been heretofore possible.
Although, for reasons of clarity, the preceding discussion has been directed primarily to the use of liners with prosthetic legs, it should be understood that the system and method of the present invention can be used to produce a prosthetic liner for virtually any type of prosthesis. Additionally, while in one preferred embodiment the system and method of the present invention is used to produce a custom prosthetic liner having a construction like that of the Applicant's current Alpha® liner, nothing herein is meant to limit the use of the system and method of the present invention to such a construction or to any particular liner materials.